Method and apparatus of forming heat exchanger tubes

ABSTRACT

A heat exchange tube for a refrigerant-flooded evaporator includes a tube body and a plurality of channels for conveying a cooling medium therethrough located in the tube body. One or more outer wall textural elements are included at the outer wall of the tube body to improve thermal energy transfer between the cooling medium and a volume of boiling refrigerant. A method of forming a heat exchange tube for a refrigerant-flooded evaporator includes urging a billet into an extrusion section and forming the billet into two tube halves including an outer wall and an inner wall having a plurality of channel halves. A textural element is formed at one or more of the outer wall and the inner wall via one or more rotating dies, and the two tube halves are joined to form the heat exchange tube.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to heat exchangers. More specifically, the present disclosure relates to forming enhanced tubes for microchannel heat exchangers.

Present microchannel heat exchanger systems are refrigerant to air applications. These systems include a plurality of microchannel tubes, typically formed of aluminum. The tubes each contain a number of channels or ports through which a flow of refrigerant is circulated. Thermal energy from the refrigerant flow is dissipated to an airflow, typically in a cross-flow orientation relative to the flow in the tubes. Such microchannel heat exchangers are typically applied to motor vehicle cooling systems.

Typical industrial air conditioning and refrigeration systems include a refrigerant evaporator or chiller. Chillers remove heat from a cooling medium that enters the unit, and deliver refreshed cooling medium to the air conditioning or refrigeration system to effect cooling of a structure, device or a given volume. Refrigerant evaporators or chillers use a liquid refrigerant or other working fluid to accomplish this task. Refrigerant evaporators or chillers lower the temperature of a cooling medium, such as water or other fluid, below that which could be obtained from ambient conditions.

One type of chiller is a flooded chiller, which typically includes a number of typically round heat exchange tubes submerged in a volume of a two-phase boiling refrigerant, having a specified boiling temperature. A cooling medium, often water, is processed by the chiller. The cooling medium enters the evaporator and is delivered to the heat exchange tubes. The cooling medium passing through the tubes releases its thermal energy to the boiling refrigerant.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a heat exchange tube for a refrigerant-flooded evaporator includes a tube body and a plurality of channels for conveying a cooling medium therethrough located in the tube body. One or more outer wall textural elements are included at the outer wall of the tube body to improve thermal energy transfer between the cooling medium and a volume of boiling refrigerant.

According to another aspect of the invention, a refrigerant-flooded evaporator includes a volume of two-phase refrigerant and a plurality of heat exchange tubes submerged in the volume of refrigerant. At least one heat exchange tube of the plurality of heat exchange tubes includes a tube body and a plurality of channels having a cooling medium flowing therethrough located in the tube body. One or more outer wall textural elements are located at the outer wall of the tube body to improve thermal energy transfer between the cooling medium and the volume of two-phase refrigerant.

According to yet another aspect of the invention, a method of forming a heat exchange tube for a refrigerant-flooded evaporator includes urging a billet into an extruded section and forming the billet into two tube halves including an outer wall and an inner wall having a plurality of channel halves. A textural element is formed at one or more of the outer wall and the inner wall via one or more rotating dies, and the two tube halves are joined to form the heat exchange tube.

These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic view of a method of forming a heat exchange tube;

FIG. 2 is a perspective view of an embodiment of a heat exchange tube;

FIG. 3 is a perspective view of a heat exchange tube half;

FIG. 4 is a schematic of textural elements of an inner wall of a tube half;

FIG. 5 is a schematic view of textural elements of an outer wall of a tube half; and

FIG. 6 is a schematic view of another embodiment of a method of forming a heat exchange tube.

The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Shown in FIG. 1 is a schematic of a method of forming microchannel tubes 10 for a refrigerant flooded evaporator. The method is utilized for forming the microchannel tubes 10 which, as shown in FIG. 2, include a tube body 12 that may be non-circular in shape, for example, oval or elliptical. A plurality of channels 14, or ports, is configured for refrigerant flow therethrough. The tube body 12 may include any number of channels, for example between about 2 and 20 channels. In some embodiments, the tube body 12 is about 1 inch in width and includes about 10-16 channels 14 therein. In other embodiments, the tube body may include about 4-6 channels 14 therein. It is to be appreciated that these embodiments are merely exemplary and other configurations are contemplated within the present scope.

Referring again to FIG. 1, the method begins with a billet 16 of a selected raw material. In some embodiments, the material is copper or a copper alloy, but other materials, for example, aluminum and aluminum alloys are contemplated within the scope of the present disclosure. The billet is fed into a heating section 18 in pairs by a ram 20. The billet 16 pairs are heated to a selected temperature, and then urged through an extrusion section 22, where the billet pairs 16 are shaped into tube halves 24, shown also in FIG. 3. Each tube half 24 includes an outer wall 26 and an inner wall 28 that includes a plurality of channel halves 30.

Referring again to FIG. 1 and FIG. 3, the extruded tube halves 24 are then urged through a texture section 32. The texture section 32 includes one or more rotating dies 34 affixed to bearings (not shown) and driven by separate or shared drive motors (not shown). The rotating dies 34 emboss textural elements or patterns into the outer wall 26 and/or the channel halves 30 of the tube halves 24. The tube halves 24 then proceed to a unitization section 38 where they are secured to each other such as for example by brazing or solid state diffusion bonding. It is contemplated within the scope of the current invention that other suitable joining techniques may also be used.

Referring now to FIGS. 4-5, the textural elements or patterns added to the outer wall 26 and or the channel halves 30 may take many forms. For example, as shown in FIG. 4, the inner wall 28 may be embossed with a plurality of dimples 40, or a plurality of grooves 42 or fins 44 that are configured to increase heat transfer between a cooling medium 46 flowing through the channels 14 and the outer wall 26 by improving mixing of the cooling medium 46 in the channels 14. In some embodiments, the grooves 42 or fins 44 may be arranged in a helical and/or cross-hatched pattern. As shown in FIG. 5, the textural elements on the outer wall 26 may be ridges 48, pockets 50, or other similar shape with sharp edges to improve nucleate boiling of a volume of refrigerant 52 in which the tubes 10 are submerged. Further, in some embodiments, the ridges 48 or other textures may be arranged helically of in a cross-hatched pattern on the outer wall 26.

In another embodiment, as shown in FIG. 6, the tube halves 24 are urged over a rotating die 34 which forms patterns or textures in the channel halves 30 of the tube halves 24. The tube halves 24 then proceed to the unitization section 38 where they are joined. The joined tube 10 then proceeds through another texture section 32, including more rotating dies 34 that apply textural elements or patterns to the outer wall 26 of the tube 10.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims. 

1. A heat exchange tube for a refrigerant-flooded evaporator comprising: a tube body; a plurality of channels for conveying a cooling medium therethrough disposed in the tube body; and one or more outer wall textural elements at the outer wall of the tube body to improve thermal energy transfer between the cooling medium and a volume of boiling refrigerant.
 2. The heat exchange tube of claim 1, wherein the outer wall textural elements comprise one or more ridges.
 3. The heat exchange tube of claim 1, wherein the outer wall textural elements comprise one or more pockets.
 4. The heat exchange tube of claim 1, wherein the outer wall textural elements are configured to improve nucleate boiling of the refrigerant.
 5. The heat exchange tube of claim 1, further comprising one or more inner wall textural elements disposed at at least one inner wall of the plurality of channels.
 6. The heat exchange tube of claim 5, wherein the one or more inner wall textural elements comprise one or more of dimples, grooves or fins.
 7. The heat exchange tube of claim 1, comprising about 2 to about 20 channels disposed in the tube body.
 8. The heat exchange tube of claim 7, comprising about 10 to about 16 channels disposed in the tube body.
 9. The heat exchange tube of claim 7, comprising about 4 to about 6 channels disposed in the tube body.
 10. A refrigerant-flooded evaporator comprising: a volume of two-phase refrigerant; a plurality of heat exchange tubes submerged in the volume of refrigerant, at least one heat exchange tube of the plurality of heat exchange tubes including: a tube body; a plurality of channels having a cooling medium flowing therethrough disposed in the tube body; and one or more outer wall textural elements at the outer wall of the tube body to improve thermal energy transfer between the cooling medium and the volume of two-phase refrigerant.
 11. The evaporator of claim 10, wherein the outer wall textural elements comprise one or more ridges.
 12. The evaporator of claim 10, wherein the outer wall textural elements comprise one or more pockets.
 13. The evaporator of claim 10, wherein the outer wall textural elements are configured to improve nucleate boiling of the refrigerant.
 14. The evaporator of claim 10, further comprising one or more inner wall textural elements disposed at at least one inner wall of the plurality of channels.
 15. A method of forming a heat exchange tube for a refrigerant-flooded evaporator comprising: urging a billet into an extrusion section; forming the billet into two tube halves including an outer wall and an inner wall having a plurality of channel halves; forming a textural element at one or more of the outer wall and the inner wall via one or more rotating dies; and joining the two tube halves to form the heat exchange tube.
 16. The method of claim 15 further comprising joining the tube halves by solid state diffusion bonding, brazing, or other suitable joining technique.
 17. The method of claim 15, further comprising heating the billet to a selected temperature before extruding.
 18. The method of claim 15, wherein the billet comprises one of copper, copper alloy, aluminum or aluminum alloy.
 19. The method of claim 15, wherein a textural element is formed on the outer wall of the heat exchange tube after joining of the two tube halves. 